1. Field of the Invention
The present invention relates generally to a machine for detecting leaks in an oxygen supply system, and specifically to an oxygen leakage regulator tester for testing leakage of oxygen regulators in oxygen supply equipment that uses a digital display.
2. Description of Related Art
It is well known that the partial pressure of oxygen in the atmosphere decreases with altitude. For this reason it is necessary in high altitude aircraft in order to prevent hypoxia at high altitudes to supply aircraft personnel with oxygen through an oxygen regulator including an oxygen mask and supply tube. Oxygen supply regulators in military jet aircraft provide the pilot and the crew with oxygen via breathing masks connected by a pipeline system to a centralized oxygen system. Oxygen regulator supply leaks can be harmful to the user, reduce available supply, and can create a hazardous environment. Therefore, it is necessary to test the oxygen regulating systems used in aircraft for leakage to ensure reliability and operability.
A conventional, portable analog tester for leakage detection comprises an air pump attached to an analog pressure gauge having an outlet tube connected to the device to be tested. The air pump is used to pump air into the device to be tested until pressure of a predetermined level is attained which is measured using the pressure gauge. Leakage in the system is determined by monitoring the analog pressure gauge for a drop in pressure per unit time or an analog flow meter. Typically, these devices cannot be calibrated to compensate for ambient air pressure or temperature. This type device is not always accurate in indicating leakage, given the inaccuracies of analog pressure gauges and the potential for error in reading the gauge. Analog devices are subject to ambient atmospheric pressure variations, resulting in inaccurate readings. Gas leakage in a relatively low-pressure system can often be hard to detect through visual inspection without test equipment.
Gas leak detectors are known in the prior are. U.S. Pat. No. 4,670,847 to Furuse teaches highly sophisticated equipment which bases its measurements on input reference values and computer analysis of results obtained from a sensor. Circuitry in this invention is not activated by a pressure sensor. Also, U.S. Pat. No. 4,998,434 to Asbra teaches permanently coupled equipment for testing a housing line without a manipulable pressure reservoir. In addition, U.S. Pat. No. 4,775,855 to Cox teaches a leakage detection system adapted for transportation systems such as hoses for primary and secondary fluids, such as those used in the transportation of petroleum products. U.S. Pat. No. 4,350,038 to Soncrant illustrates a machine that accepts or rejects hollow devices using pressurized air and three separate regulators of the prior art teaches a portable leak detector which is highly accurate for low pressures.
None of the prior art teaches a leak detector which has a reservoir volume for use during testing which is hand manipulable.
None of the prior art teaches a power efficient leak detector which does not use power from its power supply until it is activated manually, and is simple to operate, inexpensive to manufacture and easy to read.
Therefore, what is required is a specialized gas leakage detector for use in testing flight crew oxygen regulating equipment with little potential for error in determining the presence of leakage, which is sensitive in measuring relatively low pressures as well as fluid flow.
An oxygen leakage regulator tester for testing pilot and air crew oxygen equipment, including oxygen masks and oxygen supply hoses conventionally used aboard aircraft, allowing the expedient and accurate detection of gas leakage with high accuracy using electronic air flow sensors and a digital display.
The portable tester includes a hand-operated air pump, a pressure reservoir, an electronic air flow sensor, a plug and tube connected to the air reservoir for connection to a mask or hose, an air release valve, an electronic air pressure air sensor, a central processing unit, an LCD air pressure display, an LCD air flow display, an air pressure activated switch for turning the unit on and off, a carrying enclosure, and a battery power supply. The tester is engaged to a mask hose to be tested with the plug. The hand pump is used to increase air pressure in the mask up to 17 inches of water. Once the system is pressured, the LCD display is watched for air pressure and air flow rate. If the airflow rate is above 0.25 cm3/minute, then a leak is detected.
The hand air pump is comprised of a squeezable rubber bulb with two one-way valves installed within. When the bulb is compressed, air is forced out of the first end of the bulb and when released, air is drawn in through the second end, refilling the bulb. The first end of the bulb is connected to an air release valve and one end of the pressure reservoir by suitable tubing. The air reservoir is a bladder that maintains a volume of air at the working air pressure for a working supply of high-pressure air during the test.
The hand pump, air release valve, pressure reservoir, electronic air pressure and air flow sensors and air pressure switch are connected in fluid communication in-line, using suitable sealed tubing. The LCD air pressure and flow displays, electronic pressure and flow sensors, air pressure switch, and central processing unit are mounted within a portable housing or case which is formed by an elongated box having a lid and a handle. The housing also encloses the battery power supply.
The air pressure switch, battery power supply and central processing unit are electrically connected so that when the air pressure reaches a preset level in the test tube, the electrical switch is closed, and the central processing unit is supplied with operating power. The air pressure and flow displays are mounted visibly within the housing so that when the lid is open the gauges are viewable by the user. When the lid is closed, the gauges are protected from damage due to handling. The housing is portable and contained in a brief case sized box with an openable lid and a carrying handle.
The housing is sized for storing the hand pump, pressure reservoir and test operational air supply tubing when not in use. The aircraft oxygen supply system including mask and O2 supply hose to be tested is connected in-line to the plug end of the test tube. The hand pump is used to create increased air pressure (17 inches) within the mask hose or hose being tested from the high-pressure air in the reservoir. The air pressure switch closes the circuit between the central processing unit and the battery power supply, giving the central processing unit and LCD displays operating power. Fluid pressure and airflow can then be observed by reading the LCD pressure and flow displays. Leakage can be determined if the air flow display quantified air flow LCD reading exceeds an acceptable predetermined limit, such as 0.25 cm3/minute.
It is an object of this invention to provide an accurate, easy-to-read air leakage detector used for testing oxygen supply equipment which measures test air pressure and air fluid flow utilizing LCD displays while testing the actual equipment.
It is a further object of this invention to provide a leakage detector which is accurate for low leakage flow rates.